In general, a washing machine is a device for decontaminating clothes, bedding, and the like, (referred to as ‘laundry’, hereinafter) by using water, a detergent, and a mechanical operation through processes such as washing, rinsing, spin-drying, and the like, to thus clean the laundry.
Washing machines are classified into an agitator type washing machine, a pulsator type washing machine, and a drum type washing machine.
The agitator type washing machine performs washing by horizontally rotating a washing bar rising at the center of a washing tub. The pulsator type washing machine performs washing by using frictional force between a water stream and laundry generated by horizontally rotating a rotary blade having a disk-like shape formed at a lower portion of a washing tub. The drum type washing machine performs washing by putting water, a detergent, and laundry into the interior of a drum and then rotating the drum.
In the drum type washing machine, a tub accommodating washing water is mounted within a cabinet forming an external appearance, a drum accommodating laundry is disposed at an inner side of the tub, a motor for rotating the drum is mounted at a rear side of the tub, and a drive shaft connected to a rear side of the drum through the tub is axially installed at the motor. A lifter is mounted within the drum to draw up laundry when the drum is rotated.
In such a washing machine, a phenomenon in which laundry is entangled to be inclined to one side occurs, causing eccentricity such that one side becomes heavier based on the center of the drum. When the drum is rotated at a high speed with the laundry disposed partially (i.e., lopsided or unbalanced) therein (e.g., when the laundry is spin-dried), vibration and noise are generated due to unbalancing resulting from a discrepancy between the geometrical center of a rotational shaft of the drum and the actual center of gravity. In order to reduce such vibration and noise, a device, which is called a balancer, for reducing unbalancing of the drum is installed.
As a balancer for a drum type washing machine, a counter weight that corrects partial disposition (eccentricity) by attaching additional mass has been used, but recently, a ball balancer configured by forming an annular space having a certain breadth in a circumferential direction on a front surface or a rear surface of the drum, inserting balls into the space, filling the space with a liquid, and then, completely hermetically closing the space through heat fusion is commonly employed. When the drum is rotated at a high speed, the ball balancer is distributed to allow an internal material to move to the opposite side of the center of gravity of laundry, thus making the center of gravity of the drum close to the center of rotation.
However, such a ball balancer is passively rotated according to a rotation of the drum, having a problem in which the balancer cannot be disposed at a desired position.